Numerous N.sup.6 - carbamoyl and -carbonyl purines have been prepared, eg, Giner-Sorolla et al, J. Am. Chem. Soc. 80, 3932 (1958) and A. S. Jones et al, Tetrahedron Letters 26,791 (1970). The ureidopurines N-(purin-6-ylcarbamoyl) threonine, N-(purin-6-ylmethylcarbamoyl) threonine and N(purin-6-ylcarbamoyl) glycine have been found to occur naturally as their riboside in tRNA. See G. B. Chedda et al, Biochem. 8, 3278 (1969), M. P. Schweizer et al, ibid.,8, 3283 (1969). M. P. Schweizer et al, ibid., 40, 1046 (1970) and H. Ishikura, Biochem. Biophys. Res. Commun. 37, 90 (1969). N-(purin-6-ylcarbamoyl) threonine has also been identified in human urine. G. B. Chedda, Life Sci. 8, 979 (1969). Several ureidopurine derivatives related to N-(purin-6-ylcarbamoyl) threonine have been synthesized and found to have cytokinin like growth-promoting properties. See C. I. Hong et al, J. Med. Chem. 16, 139 (1973) and R. H. Hall et al, Cancer Res. 31, 704 (1971). C. I. Hong et al, Abstracts, 162d Am. Chem. Soc. Nat'l. Meeting, Wash. D.C. (Sept 1971) have prepared 5'-phosphates of a number of naturally occuring 6-ureidopurine nucleosides, including those of structure ##STR1## wherein R was alkyl or aryl. Adenosine 3', 5'-cyclic phosphate (cAMP, 1) has been well established as a mediator of many hormonal effects, and numerous of its 8-substituted derivatives have been prepared and demonstrated to possess physiological activity. Eg, U.S. Pat. No. 3,712,885 to Weimann et al.
According to this invention, there are prepared novel cyclic nucleotides of structure ##STR2## wherein Y is COOR.sub.1, CONHR.sub.1 or CONHC.sub.6 H.sub.5, X is acyl, H or Y, Z is H, halogen or SR.sub.2, R.sub.1 is C.sub.1 - C.sub.6 alkyl and R.sub.2 is H, phenyl, benzyl or C.sub.1 - C.sub.6 alkyl. The manner in which these compounds with the advantage of their properties previously referred to are obtained will appear from the detailed description which follows.